Method of catalytic cracking



Patented May 25 1948 METHOD OF CATALYTIC CRACKING William A. Pardee, Pittsburgh, and Charles W.

- Montgomery, Oakmont, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application June 22, 1945,

Serial No. 601,072 1 7 Claims. 1

This invention relates to an improved method of catalytic cracking, and more particularly it relates to the conversion of a hydrocarbon oil into gasoline by the use of a catalyst.

The art of convertinghigher boiling Point hydrocarbons into hydrocarbons of a low boiling point such as gasoline is well known. Thermal conversion has long been practiced but more recently cracking by the use of catalysts has been introduced. As catalysts, aluminum oxide, molybdenum oxide, clays and synthetic silica-alumina compounds have been used. Another catalyst which has been mentioned in the prior art is a hydrated magnesium silicate-calcium silicate compound.

The more recently constructed gasoline engines are designed for a higher octane gasoline than is sometimes produced by the prior art conversion processes. Gasolines of lower octane rating may have their octane rating increased by the addition of suchingredients as tetraethyl .lead, but it is desirable that the gasoline as originally produced be as high in octane number as possible. One of the factors contributing to high octane rating, particularly high road octane rating at low to moderate speeds, is a high olefin content especially in the lower boiling 50 per cent and it is therefore desirable to attain a high olefin content in the conversion product.

It is therefore an object of this invention to produce a gasoline of high olefin content and high anti-knock quality by the catalytic conversion of a hydrocarbon oil.

It is a further object of this invention to produce a high yield of gasoline from a hydrocarbon oil.

It is a further object of this invention to produce a high conversion of hydrocarbon oil to gasoline while producing a small amount of gas and coke.

These and other objects are attained by the discovery that the hydrated magnesium silicatecalcium silicate compound described herein under certain operating conditions yields a high olefin content-high octane rating gasoline from gas oil cracking. The primary conditions yielding such conversion are that the space velocity be between 3 and 6 and preferably about 4. As used herein space velocity will be expressed as volumes of reactant per volume of catalyst per hour.

Thus, in general it has been found that the use of a space velocity of about 4 gives a gasoline product having a bromine number which is considerably higher than that obtained at, say, a space velocity of 1 or 2. Below a space velocity or 3 the bromine number falls oif sharply and above a space velocity of 6 the bromine number remains about the same, but the conversion of gas oil to gasoline drops of! so that it is not desirable to go to still higher space velocities. By the use of this process a high ultimate yield of high olefin content gasoline is obtained with a smaller gas and coke formation than is obtained in the usual catalytic processes. High space velocities are usually avoided because they lower the once throughconversion to gasoline but by recycling it has been found that the ultimate yield is even greater than with the prior art.

The invention is illustrated by the following examples:

Example I A quantity of Pennsylvania gas oil was placed in contact with the herein described magnesium silicate-calcium silicate compound in a catalytic cracking chamber which was operated at a temperature of about 950 F., a space velocity of 3.0 volumes of gas oil per volume of catalyst per hour and a throughput per cycle of 1.0 volumes of gas oil per volume Of catalyst for a total of 36 cycles. 23.5 per cent of the gas oil on a weight basis is converted and the yields are given in the following table:

The octane number of the gasoline product, motor method, was 18.1 and with 3 cc. of tetraethyl lead per gallon it was 83.3. The bromine number of the gasoline product was 128.3 as compared with 3.9 for the charging stock.

Example II In a run similar to Example I at a temperature of 950 F. but at a space velocity of 6 volumes of gas oil per volume of catalyst per hour a gasoline weight per cent of 18 was obtained while the gasoline bromine number was 150.

The process of conversion may be carried on by any of a number of methods well known to the prior art of catalytic cracking. Also. the epparatus which is used may vary and the m is adaptable to many types of apparatus known to those skilled in the art.

The catalyst is a hydrated magnesium silicatecalcium silicate compound produced by the reaction of a hot solution of magnesium salt or a strong acid upon calcium silicate for a time sumcient to eifect only a partial conversion of the calcium silicate to magnesium silicate. The catalyst is more specifically described in U. 8. Patent 2,163,525 to Lyle Caldwell. It has been found most preferable to use the catalyst in a granular form.

The temperature of the reaction should be from 925" to 1000 F. and preferably 950 F. The

pressure may be atmospheric pressure but it is possible to use increased pressures as well.

The charging stock has been described as a hydrocarbon oil and it may be any such oil ordinarily subjected to cracking for gasoline such as kerosene, gas oil, fuel oil, topped crude, etc., but the process is particularly adaptable to gas oil conversion.

Thus we have described a new process for converting hydrocarbon oil to a high olefin content gasoline with a high ultimate yield of such gasoline and a low gas-coke formation.

What we claim is:

1. A process for producing high olefin content gasoline from hydrocarbon oil which comprises subjecting the hydrocarbon oil under catalytic cracking conditions to contact with a. catalyst comprising a hydrated magnesium silicate-calcium silicate compound at a space velocity of from 3 to 6.

2. A process for producing high olefin content gasoline from hydrocarbon oil which com prises subjecting the hydrocarbon oil under catalytic cracking conditions to contact with a subjecting the hydrocarbon oil under catalyticcracking conditions to'contact with a catalyst comprising a hydrated magnesium silicate-caicium silicate compound at a space velocity or 4.

5. A process for producing high olefin content gasoline from hydrocsrbon'oil which comprises subjecting the hydrocarbon oil under catalytic cracking conditions to contact with a catalyst cium silicate compound at a space velocity of Irom 3 to 6 and at a. temperature of about 950 F.

6. A process for producing high olefin content gasoline from gas oil which comprises subjecting the gas oil under catalytic cracking conditions to contact with a catalyst comprising hydrated magnesium silicate-calcium silicate compound at a space velocity of about 4, and a temperature of about 950 F.

7. A process for producing high olefin content gasoline from hydrocarbon oil which comprises subjecting the hydrocarbon oil under catalytic cracking conditions to contact with a catalyst comprising a hydrated-magnesium silicate-cal- 80 cium silicate compound -at a space velocity 01' from 3 to 6 and at a temperature or from about 925 to 1000 F.. said compound having a granular form.

WILLIAM A. PARDEE.

35 CHARLES W. MONTGOMERY.

REFERENCES CITED The following references are of record in the 40 file of this patent:

UNITED STATES 'RATENTS Number "Name Date 1,732,381 Schmidt et ai. Oct. 22, 1929 5 1,802,628 Caldwell Apr. 28, 1931 4 .az'zasco Ruthrufl Apr. 7, 1942 2,350,282 Lamnde May 30, 194d 2,390,550 Ruthrufl' Dec. 11, 1945 comprising a hydrated magnesium silicate-cal- 

